Electrical translating device



March 21, 1933. J. s, H1@ 1,902,643

ELECTRICAL TRANSLATING DEVICE Filed Oct. 30, 1950 2 Sheets-Sheet i INVENTOR March 21, 1933. *y H|GH i `ELECTRICAI.: TRANSLATING' DEVICE Filed Oct. 50 '1930 2 Sheets-Sheet 2 INVENTOR i JzUyILSy/Y ATTORNEY atented Mar. 2li, 1933 i UNiIEo4 STATES JUEJEN s. HIGH, or CAKLYN MANOR, NEW JERSEY, AssI'GNoE'ro WEsrINGIIoUsE ELEC- l' TRIO & MANUFACTURING COMPANY, A CoEroR-A'rIoN or PENNSYLVANIA ELECTRICAL IEANSLATING DEVICE Application :filed October 30, 1930. Serial No. 492,215.

My invention relates to electrical translating devices and it has particular relation to devices of the type known as loud-speakers. i

Substantially all loud-speakers, as hitherto constructed, may be divided into three main classes, i. e.,'those wherein the movable element of the motoris a coil, or the like, those in which a movable metallic armature is mounted to oscillate in a magnetic field and those wherein a metallic diaphragm is subjected Vto avarying magnetic attraction. Loud speakers of the first-mentioned class, generally known as electrodynamic speakers, are, for many reasons well known to those skilled in the art, acoustically superior tov loud speakers o'l' the second and third classes.v y

l Electrodynamic speakers, however, are relatively bulky and clumsy, and are quite 'eX- pensive to' manufacture. Furthermore, such speakers must either be provided with relatively massive tield-magnets of cobalt steel, or else have a large held-winding capable of being energized from a direct current source.

They usually require aspecial input transformer for furnishing the'optimum sound current and, if they are of the type having a eld winding, a rectifying device is nec-v essary for converting the commercially available alternating current into direct current for the field. y

The held-magnet structure of the usual electrodynami'c loud speaker occupies a space extendingve inches, or more, rearwardly of the apeX of the cone-diaphragm, necessitating the use of a deep enclosing case,

which is objectionable on account ofl the ydistortion introduced by case resonance.

In short, electrodynamic speakers, by reason of their unavoidable bulkiness Aand Weight, have not been at'all suitable for Wall mounting and, as a consequence, the majority of loud speakers of the wall-type have com- 4" prised balanced-armature motors.

It is, accordingly, an object of my invention to provide an `electrodynamic loudspeaker motor particularly suitable for use in wall-type loud speakers. Y

Another object of my invention is to provide anV electrodynamic loud-speaker motor that shall be much shallower, when considered axially of a conical diaphragm actuated thereby, than previously constructed motors of the same genera-l type.

Another object of my invention is" to provide an electrodynamic loud-speaker motor that shall be relatively inexpensive to manufacture.V Y K Another object of my invention is to provide a loud-speaker motor, of the induction type, wherein the moving element is .so constructed and arranged that efcient use isv made of the induced currents flowing therein.

Anotherv object of my inventionY is to prot vide a loud-speaker motor that shall be substantially unaffected by uctuations in the current supplied' to the field-Winding thereof.

Another object of my invention .is to provide, in a loud speaker motor, means whereby the magnetic iiuxarising, from variable currents, representing sounds, shall be conned to a limited magnetic circuit that is substantially independent of the field-magnet', whereby the said ield magnet is prevented from rapidlyl losing Vits magnetization'. i

Another, and m-ore specific. object of my invention, is to provide a unitary moving element and resilient support'therefor suitable for use in my improved electrodynamic. loud speaker. l

According to my invention I provide a U- shape permanent magnet of chromium or cobalt steel, or an electromagnet, with a plurality of laminated pole-pieces. The `polepieces closely approach one another to deine a narrow air-gap in which is resiliently suspended a thin plate of non-magnetic material. v Each pole-piece is provided with a soundcurrent coil whereby the luX threading the thin plate may be caused to vary and, accord-A ingly, to induce potentials therein which give rise to electric currents. Theplate, which hereinafter will be designated the'armature, is connected to a diaphragm ofany convenient configuration, such as a cone,'or the like, by means of la connecting rodv soldered therey to or formed as an integral extension thereof.k v The novel features that I consider characv particularity in the appended claims.

teristic ofmy invention are set forth with l The invention itself, however, both as to itsv organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment, when read in connection with the laccempanying drawings, in which Figure 1 is a plan View of a loud-speaker actuating motor comprising a preferred embodiment of my invention;V f

Fig. 2 is an end elevationalV view of the motor;` f

Fig. 3 is a side elevational view of the same;

' Figs. e and 5 are views of an armature illustrating the manner in which electric currents are constrained to liow therein;

- Fig. 6 is a view in perspective of an armature as disclosed in Figs. l and 5;

Figli?. a plan'view partially in section, illustrating a modification of my invention as disclosed in Fig. 1;

Fig. 8 is a cross sectional view along the line Vlll-llll of Fig. 7 with the diaphragm removed;

Fig. 9 is a view showing an armature structure for use in the embodiment of my invention as disclosed in Fig. 7

Figs. l() and 11 are views illustrating the manner of'supporting or mounting an armature of the type disclosed in Fig. 9;

Fig. 12 is a schematic view showing a modification of the armature supporting means vdisclosed in Figs. l() and 11.

, The. apparatus illustrated in Figs. 1, 2 and 3 comprises a ll-shape permanent lield magnet 1 preferably of cobalt steel or of an equivv alentmaterial. Each pole of the magnet 1 is provided with pole-piece assembly constituted by a plurality of h-shape laminations 2 of silicon steel. y Each stack of laminations constituting a pole-piece is held firmly against the corresponding end of the permanent magnet by means of aclamping bolt 3 which extends through the said end and which is yprovided with a retaining device l having. downwardly-bent ends 5. The laminated pole-pieces are so disposed with respect to each other that a plurality of narrow rectangular air gaps 6 and Z are defined by the inwardly extending legs 8, 10, 11 and l2 thereof.

A. voice-coil 18 is mounted upon and encircles a member of each of the pole-pieces defined by the several crossbars 14 of the laminations, as clearly illustrated in Fig. 2. The'voice-coils are so wound and interconnect'ed that the magneto-motive forces engendered thereby are always in series-aiding relation, insofar as the magnetic circuit comprising the elements 8, 10, l2 and 11 of the laminated pole-pieces are concerned, when The varying' voice-currents flow therein. flux is confined entirely to the pole-pieces,

the direction thereof corresponding to. one direction of voiceecurrents flow. being indicated in Fig. 2 by the arrows 15, and does not traverse the held-magnet. f

Conversely, a variation in the flux from the ieldemagnet, in the event thattlie magn net is provided with a field-winding, or otherwise, will not induce electric-currents in the armature in such directions as to cause a movement thereof longitudinally of the gap.y

Each of the outermost laminations or end plates of the pole-piece assemblies 2 is provided with a projecting lug 16. Y

A thin, flat armature i7 of conductive, non magnetic metal is resiliently mounted in the air-gaps 6 and 7, defined by the pole-pieces 2, the mounting means for the armature. being constituted by a plurality @farms 18 integral Varms 18 are aligned with corresponding openings in the lugs 16 provided on the out* ermost laminations of each pole-piece assembly. A clamping bolt 23 extends through.V

each pair of align-ed openings. `Electrical Contact between the arms 18 andthe lugs 16 is prevented by surrounding each of the clamping bolts 23 with an insulating bushing 24. The openings 22` in the arms 18 are made slightly grcaterin. diameter than the bolts 23, in order that vthe armature maybe easily centered in the air-gaps- Y The armature is provided with a plurality will hereinafter 'be referred to, orit may be of elongated openings 8() fer a purpose whichv so made thatfthe openings are substantially Y semi-ovals, as shown in Fig. 9. t

One edge of the armature 1s provided'with a lug 31 to which a metal cup 82, or a spider,l may be soldered for the purpose of imparting,

motion to a diaphragm 38. Y

yWhen the voice-coils 13 of my improved loud-speaker motor, are energized from any convenient source of alternating currents, at audio-frequencies, potentials are so induced in the armature 17 that electric-currents tend' closed through the portions of the armature defined by the openings 80 as sho-wn by the arrows in Fig. 4. The circuit therefor being closed through the portions of the armature between the openings and the upper and lower edges of the said armature, additional eddy-currents (illustrated in Fig. 5) also tend, instantaneously,- to flow across these outer portions of the' armature.V The additional eddy currents, however, asillustrated ways in the samefdirection, in each of the airgaps the reaction between the said flux and the electric-currents in those portions of the armature intermediate the extensions of the pole-pieces is in aiding phase. The armature, accordingly, moves either up or down,

dependingupon the instantaneous directionv of the voice-current which induces the elec# tric-currents therein, at the frequency of the said voice-currents andV with force propor.

tional to the intensity thereof.

Inv the modification illustrated in Fig. 7, I have disclosed a simplified structure capable of opera-ting on the same principles as that of Fig. l. The magnet structure is laminated and built up of L-shaped transformersteell punchings interleaved to form a substantially closed magnetic path except for a narrow air gap wherein to support'anarmature of the type disclosed in Fig. 8. The armature e referred'to comprises a punching from a thin sheet of preferably non-magnetic material such as copper or aluminum and of substantially the shape shown. A slot in thearmature along its longer axis divides the arma- Vture into substantially two sections andacts as an open circuit to thepassage of ed-dy currents whichare proneto develop inta 4system as shown. 1 z

In the armature disclosed in F ig'. 9, amore efficient means is provided for .opposing the development of eddy currentstherein. This comprises the provision of a plurality of concentric narrow slits 39'of horse shoe shape terminating close to lthe center line of the armature. This construction permits of the armature being punched asa one piece affair. The unbroken center line portion of the arma- 'ture will not destroy'the effect sought fto be obtained by the slitt-ed structure because the potentials induced at points along the center line are of the same potential and consequently no eddy currents vwill be caused to flow. l

Another method of constructingan armature to give similar results is to wind narrow flat ribbon wire into a single layer pancake coil of a size comparable to thatI of an arma ture, a thin solution lof water glass or other insulating material being interposed between i turns of the wire to perform the function attributed to the slits in the punched armatures described above.

As remarked inconjunction with the description of the structure of Fig. 7 and its component parts, the armature 36 is provided with a stem 38 upon which to mount a diaphragm40`of any desired type. Inthe'ribl-- i bon'v woundftype of armature,the stemmay extend-across and be embeddedin thelsur-4 face of the armature toadd to the mechanical strength ofthe structure.

In lassembling the 4sp A edinFig. 7, the armature 36 -is suspended in the air gap with its'upper `half opposite the pole faces. Y i

-A pair of serially connected coils 41v and 43 are mounted, one onleach pole pie'ceas shown.V The-structure so faras described is with microphonic pick up devices for phono-, graphs or the like wherein `the directjcurrent or polarlzing-component is of alcompara'tively large directcurrent or polarizingcom-V ponent present, it is `entirely feasible to pass both currents through the c oilsofthemotor and obtain eiiicient results;

' When employed,however, in connection with radio receiving sets or vthe like, itis not advisable to pass bothythe polarizingandy u i voice current through the same coils.: The

direct" current component in this case would -be of the order of 1/50 of an ampere, so thatv a coilfof considerably larger number ofturns u would be required .to create the desired num-` ber'of ampere turns for polarizing purposes. Sucha, large number of turns would increase the vcoefficient of self:A induction to such an extent as to render it yunfit as avoicefcoil.

may be employed as a polarizing coil where-l as the othercoil may be designedV asa' voice coil. Y a y n f Theembodiment wherein apairof voice coils is utilized, is admira-bly adapted for use, with radio recelvers employing a stage of Vpush-pull amplification.r When so employed,

each coil will comprise the load on one ofthe tubes, which tubes are inl'push-pull-arrangement. The voice coils may be either yconu fm eaker motor illustrat- 'very suitable when employed in'combination ly large magnitude, of the .order of one'a-m-v pereor so. Thecircuit arrangement would nected directly in Vthe plate circuit ofthe tubes or be inductively coupledthereto.l 1 f One means of supporting the armature `in itsv proper position within the air' gap of the device illustrated in Fig. 7 is disclosed, in Figs. 10 and 11 of the drawings. Y .v y

The armature indicated'by the reference numeral (36) is held in spaced relationship to the pole `faces by, means of'strips 45 ofv suitable fibrous material, mounted on the pole `pieces vatdesirable locations. Among the materials suitable for` the purpose may be mentioned loose graphited textile o1v felt,

iso

the graphite serving'as a dry lubricant.,V- 'I he strips' referred to .-'above may comprise two partsone of which serves to space :the armature with` respect to a pole face and the other part'functions to prevent ,axial shiftsV of the armature. w Elements 47 ofinsulating material riveted or otherwise secured Vto the arma-, ture serve to clamp` the fibrous strips to maintain them in their proper position.

An alternative method of supportingthel armature 36 in operative position vis disclosed in Fig. 12. This differs from that disclosed with reference to Figs. and 11 in that the spacing strips may be kattached rto the armature 36 and in lieu ofthe clamping elements 47, ytwo'strings 49 of proper lengthV may be attached, one at each end of the armature l which' accommodate amovable coil. TherebyV a smaller amount of magnet steel is required. t.

:A loud-speaker motor constructed according to my invention is, further, quite advan tageous in that it may begiven la total thicknessy notsubstantially greater thanthe thick f ness yof the fixed magnet portion thereof.

This peculiarity of `construction is `an im,-

- portant feature of my invention inasmuch as it enables the manufacture of a loud-speaker,

the front to back dimension of which may be made suficiently smallV to adapt the device for wall mounting, even though it is entirely enclosed in a cabinet or the like.

Although I have shown and described certain specific embodiments of my invention,

l I am fully aware thatmany modifications .thereof are possible. My invention, therefore, is not to be restricted except insofar'as is necessitated bythe prior artand by the spirit of the appended claims;

I claimas my invention: l

1. yIn combination, a magnetic structure comprising a ixedf magnet and a plurality of laminated pole-tips defining a narrow,

substantially rectangular air gap, a coil associated vwith each poletip and a'substantially flat, lnon-magnetic, conductive armaL ture mounted in said air gap for movemen longitudinallyl thereof. Y

2. An armature for a loudspeaker motor comprising a substantially fla-t, conductive element of non-magnetic lmaterial. provided with integral supporting` lugs extending outwardly from the edgesthereof, said lugseach having a rigid portion anda flexible portion,

rectangular air gap, each polepiece being constituted by a plurality of h-tshape lamina# tions, and a coil individual to eachpole piece,

each coil being disposed around the element of its associated pole piece-defined by the cross bars of the h-,shape laminations therefVv 5. In a loud-speaker actuating motor, apermanent magnet, a plurality of laminated., hshape pole pieces 'aflixedto said magnet, the laminations ofsaidpole pieces being soV disposed withvrespect to each otherl asto deline a'plurality of narrow substantially rec- Y tangular air gaps, and a substantially flat, conductive, no'ndnagnetic armature resiliently suspended in'said gap, said armature being provided with an elongated opening'intermediate the edges thereof.

` 6. In a loud-speaker motor, afield magnet, ik

a plurality ofpole-pieces aflixed to said mag`v net' to define an'air-gapy and means for causing `theflux in said pol-e pieces and said gap .'tovary, the configuration of vsaid pole-pieces being. such that'a substantially. complete magneticcircuit is provided thereby for the varying flux. f l

' 7. In a loud-speaker motor, a field magnet, a plurality of h-shape pole-pieces'aihxed to said magnet to define an air-gap, and means for causing the flux in lsaid pole-pieces and said gap to vary, the configuration of the said pole-pieces and their association with said magnet being such that the varying ilux is prevented from traversing the maj or portion of said lfield magnet.VVV 8. Inra .loud speakeractuating motor, a magnetic circuit defining an air gap, an armature, only va pertion of which lies in said air gap, meansfor generating a'current in that portion of saidf'armature lying outside of said air gap but parallel to the portionv in saidair-gap and meansy for directing said current into that portion'of the armature located in the air gap. f

"In testimony whereof, I have hereunto subscribed my naine this 24th day of October,

1930. t i JURJEN S. HIGH. 

